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Essential oils for fragrance: review guide

How to qualify an essential oil or other natural aromatic material before it goes into a fragrance or cosmetic: what it is, how it was made, what is in it, and the documents to ask the supplier for.

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ISO 9235:2021

Name the material with the ISO vocabulary

ISO 9235 is the international vocabulary for aromatic natural raw materials. It defines what an essential oil is and what the other natural materials are (absolutes, concretes, resinoids, oleoresins and so on). Two answers place any material: which part of the plant it comes from and which process made it. For example, lime oil obtained by cold expression of the peel is a fruit material made by expression; lime oil distilled from the juice is a different material with a different composition.

Ask the supplier to name both in ISO terms, using their copy of ISO 9235:2021. The standard is sold by ISO and national standards bodies; we do not reproduce it here.

1 · Part of the plant

Root, moss or lichen, bark, wood, leaf and twig, flower, fruit (including the peel), seed or grain, algae, exudate (gums and resins), twig or stem, animal by-products, or several parts together. The part drives the chemistry: see the Botanicals page for examples.

2 · How it was made

MaterialIn short
Essential oil, steam- or hydro-distilledVolatile oil separated from water after distillation of the plant
Essential oil, cold-expressedPressed mechanically from citrus peel at room temperature; keeps non-volatile compounds such as furocoumarins
Dry-distilled oilDistilled from wood, bark, roots or gums without water or steam (for example cade oil)
ConcreteSolvent extract of the fresh plant, solvent removed; waxy
AbsoluteEthanol extract of a concrete, resinoid or CO2 extract, dewaxed and with the ethanol removed
ResinoidSolvent extract of a dried resin, gum or balsam
Oleoresin / balsamNatural or extracted mixture of resin and volatile oil; balsams are rich in benzoic or cinnamic compounds
CO2 (supercritical) extractExtract made with carbon dioxide under pressure
Aromatic water (hydrolate)The water left after distillation, with dissolved aroma
Treated oilsFolded (concentrated), rectified, deterpenated or "free from" grades, such as furocoumarin-free bergamot: a further physical step changes the composition

Plain-language summaries for orientation; the ISO definitions are the reference.

3 · What to ask the supplier

One questionnaire per material and supplier code, every field answered or marked "not applicable" with a reason, signed by the supplier and countersigned by their quality function.

TopicWhat to collect
SupplierLegal name, manufacturing site and country, contact; US FDA facility registration (MoCRA) where applicable
IdentityProduct name and code, INCI name, botanical (Latin) name and chemotype, CAS and EC numbers, FEMA number for flavor use
OriginPlant part, fresh or dried, cultivated or wild, country and region of harvest, harvest period, applicable ISO or pharmacopoeia monograph (for example ISO 3515 lavender, ISO 4730 tea tree)
ISO classificationThe ISO 9235 plant part and processing method, one primary method, plus any secondary treatment
ProcessDescription and flow chart from plant to packed material; time, temperature and pressure; post-treatments; solvents and residual solvent levels
CompositionGC-MS profile with the full chromatogram (peaks from 0.1% identified), main constituents, carrier or diluent, any antioxidant
Added substancesYes/no answers on synthetic or nature-identical chemicals, isolates, other oils, carriers and solvents; every "yes" listed with CAS, function, origin and %
TraceabilityGrower or collector, distiller, every company that owned the material, and how the lot number links to the production batch
Fragrance allergensAllergen statement with the typical % of each of the 81 EU allergens present
ContaminantsHeavy metals (Pb, As, Cd, Hg), pesticide residues, and microbiology where relevant
IFRAIFRA Conformity Certificate with the amendment number and date; any IFRA Standard restrictions
Claims supportOrganic certificates, ISO 16128 natural origin index, GMO status, kosher / halal, vegan, sustainability certificates
Quality systemISO 22716, ISO 9001 or cGMP; last audit; open FDA warning letters or 483s
StorageStorage conditions, shelf life unopened and opened, stability data
DocumentsCOA, SDS, technical data sheet, GC-MS, chromatogram, flow chart, chiral GC and carbon-14 reports where required

4 · Is it authentic?

  • Compare the GC-MS with the monograph: the main constituents should fall inside the ranges of the ISO or pharmacopoeia monograph for that oil.
  • Chiral GC: natural oils have typical ratios of mirror-image forms (for example of linalool or limonene); synthetic additions often shift them.
  • Carbon-14 (ASTM D6866): petroleum-derived carbon has no carbon-14, so the test shows added synthetic material.
  • Stable isotope ratios: help tell sources and adulteration apart when the other tests are not conclusive.
  • Re-qualify when the source, process, site or specification changes, and on a fixed schedule.